Added gamma correction to tcl server.

I decided to try to address the gamma correction issue with TCL pixels the way I had in the elinux-tcl library. I basically create a lookup table for each color (right now that's not really used, but it could potentially come in handy) and I create the gamma correction table before the server starts.

I'm working on some other arduino based LED projects, so I don't have a test harness set up for this at the moment, but I hope it's not buggy.